Conventionally, as navigation equipments, electronic nautical chart display systems have been known, which include systems so called ECDIS (Electronic Chart Display and Information System) and ECS (Electronic Chart System). These systems display electronic nautical charts on a computer screen based on electronic nautical chart data.
Electronic nautical charts are generally purchased separately from electronic chart display systems themselves. Such electronic nautical charts are electronic data created based on measurement data from waterways authorities and information illustrated on paper nautical charts. Therefore, each electronic nautical chart is recorded with a different range of marine areas and has different level of detail in recorded data. There published various electronic nautical charts for different recorded ranges and with different levels in details, for various marine areas in the world. Users can choose the electronic nautical chart which he himself or she herself needs, and purchase and acquire (download) to use it. The unit of data of electronic nautical chart that can be acquired by a user in one acquisition is herein referred to as “acquisition unit.”
When the user purchases the electronic nautical chart, he/she acquires data of the electronic nautical chart and installs it into an electronic nautical chart display system. The user also acquires a license of the purchased electronic nautical chart. Only when the electronic nautical chart data is installed into the electronic nautical chart system and the license of the electronic nautical chart is valid, the chart can be used.
In this regard, JP2003-005630A, although it is not related to an electronic nautical chart, discloses a navigation device with which a user can use, by selecting an area to purchase from a range which is sectionalized in advance, map data corresponding to the selected area.
As described above, the use of the electronic nautical chart display system can purchase and acquire (download) an acquisition unit of the electronic nautical chart at a time. However, when a plurality of electronic nautical charts are purchased and the number of purchased electronic nautical charts is excessive, it is difficult for the user to grasp whether the data of each electronic nautical chart has been installed, and whether the license of each electronic nautical chart has been acquired.
In addition, each electronic nautical chart is periodically updated and update information is provided thereto. For the safety of navigation, it is desired that the electronic nautical chart is updated to the latest version. However, when a plurality of electronic nautical charts is purchased and the number of electronic nautical charts is excessive, it is difficult for the user to grasp whether each electronic nautical chart has been updated.
Moreover, since various kinds of electronic nautical charts for different recorded ranges and with different levels in details are prepared, it may be required to purchase more than one kind of electronic nautical chart per marine area. For example, when calling at a port during ocean navigation, in addition to a nautical chart for a wide range, a detailed nautical chart for the inside of the port will also be needed. However, when a number of electronic nautical charts are required, it may be difficult for the user to grasp which electronic nautical chart has already been purchased. Therefore when newly purchasing an electronic nautical chart, it may be difficult for the user to determine which electronic nautical chart should be purchased.
Thus, since various kinds of electronic nautical charts with different recorded ranges and levels in details are individually provided to the electronic nautical chart display system, it is extremely difficult for the user to accurately grasp the status of the purchased electronic nautical charts (e.g., whether the data has been acquired, whether the license has been acquired, or whether the data has been updated). In this regard, the navigation device disclosed in JP2003-005630A has the configuration in which the one kind of map data which is installed in the device in advance is sectionalized, and the user chooses an area to use from the map data; therefore, it is considered that there is no difficulty for the user to grasp the purchased map data in particular. However, there is no description in JP2003-005630A in view of facilitating the grasp of the purchased map data by the user, in the first place.